ISIS has claimed responsibility for the attack at an Ariana Grande concert in Manchester in the UK.

On May 22, an explosion occurred at the end of an Ariana Grande concert at the Manchester Arena in the United Kingdom. It has been reported that 22 people were killed and at least 59 more were injured in the attack. The day after the bombing, the terrorist group known as the Islamic State (ISIS) claimed responsibility for the attack, saying that "one of the soldiers of the Caliphate was able to place an explosive device within a gathering of the Crusaders in the city of Manchester." The British government hasn't publicly commented on the claim.

In 2011, a civil war broke out in Syria in response to efforts to overthrow dictator Bashar al-Assad. ISIS quickly took advantage of the chaos. The group now controls a vast territory in Syria and Iraq. It has become one of the largest, most successful, and most violent groups operating in Syria and Iraq. It executes prisoners of war and enslaves minorities, and its members have raped thousands of women and young girls.

The group’s violence also extends even to the day-to-day tasks of governance. Criminal penalties in territory controlled by ISIS can include stoning, amputation, and even crucifixion.

Why:

ISIS hopes to establish what they view as a “pure” Islamic state or a "global caliphate" — despite the fact that the overwhelming majority of the world’s Muslims reject ISIS and its version of Islam. The group paints the world in black and white — with them or against them.

This means that the mission of ISIS is not just to convert people but to get rid of "disbelievers," often through violent means. "This is a duty upon the Muslims — a duty that has been lost for centuries.... The Muslims sin by losing it, and they must always seek to establish it," Baghdadi has said in the past.

What:

Like Al Qaeda, ISIS embraces a violent and hardline version of Islam that it uses to justify acts of terror against civilians around the world. The group has been responsible for thousands of civilian deaths worldwide — mostly against Muslims in Syria and Iraq. While it's hard to put exact numbers on the damage ISIS has caused, ISIS-linked events in Iraq alone are estimated to be responsible for roughly 18,800 deaths in the past two years. This also doesn't take into account the number of people who've been displaced or had their safety in jeopardy because of ISIS.

Unlike Al Qaeda, ISIS believes the world is headed toward a final battle between Muslims (them) and non-Muslims (everyone else). Not everyone who fights with ISIS believes that. Many have joined out of desperation, economic necessity, coercion, or a misguided sense of adventure. But many foreigners who join ISIS do embrace the group’s twisted interpretation of Islam.

It’s important to remember that groups like ISIS and Al Qaeda do not represent the 1.6 billion Muslims in the world, even if they want to.

Planning these attacks at the headquarters in Syria would make ISIS a lot like Al Qaeda — a top-down international organization. But the group also encourages supporters to carry out attacks in its name without asking permission. There have already been several of these “lone-wolf” attacks. Anyone with an Internet connection can participate. That makes ISIS less like an organization and more like a virus.

In the case of the attack in Manchester, one attacker is believed to be dead and police have arrested a 23-year-old suspect, but they are still investigating whether he acted alone or was part of a larger operation. It's still not confirmed whether he or anyone else involved had been in contact with ISIS or was inspired to act because of ISIS.